1. Field of the Invention
The present invention relates to a light guiding device and a backlight module employing the light guiding device, the backlight module typically being part of an LCD (liquid crystal display).
2. Description of Prior Art
Because an LCD device has the merits of being thin, light in weight, and drivable by a low voltage, it is extensively employed in various electronic devices.
In an LCD device, usually a backlight module having a light source and a light guiding device is used to provide the needed illumination. The light source emits light beams to the light guiding device, which then transmits the light beams to illuminate liquid crystal molecules in a liquid crystal panel. It is important that the light guiding device transmits light beams to the liquid crystal panel uniformly.
Referring to FIG. 6, an exploded, isometric view of a typical backlight module 8 is shown. The backlight module 8 comprises a light guiding plate 81, a reflection member 82, a diffusing plate 83, a converging plate 84, a light source 85, and a light source cover 86. The light guide plate 81 has a light incidence surface 811, a bottom surface 812, and a light emitting surface 813. The reflection member 82, the light guiding plate 81, the diffusing plate 83 and the converging plate 84 are stacked one upon the other in that order. The light source 85 and the light source cover 86 are disposed adjacent to the light incidence surface 811.
The light source cover 86 functions mainly as a reflection element, to ensure that most if not all of the light beams emitted from the light source 85 enter the light guide plate 81 through the light incident surface 811. The light beams are transmitted in the light guide plate 81 and reflected by the reflection member 82, and emit from the light emitting surface 813. The diffusing plate 83 diffuses the light beams so that they are more uniformly distributed. The converging plate 84 then converges the light beams to illuminate a liquid crystal panel (not shown).
Referring to FIG. 7 and FIG. 8, these are isometric views of a mobile phone 9, respectively is showing an external display 92 when the mobile phone 9 is in a folded state, and an internal display 91 when the mobile phone 9 is in an unfolded state. The backlight module 8 is not suitable for this kind of two-screen display device. Even if the reflection member 82 were removed, the backlight module 8 would not be able to provide uniform illumination at both sides thereof. If two backlight modules 8 were to be employed, the whole mobile phone 9 would be unduly thick and heavy.
It is desired to provide a new light guiding device and a corresponding backlight module which overcome the above-described problems.